Insulating material.



* glass.

rninnnrcn BoLLmG, or oBnnunsE'L, GERMANY, assrenoa or ONE-HALF TO THEFIRM or PROMETHEUS FA .BRIK ELEKTRISCHER KOCH; nun HEIZAPPARATE,GESELLSCHAFT MIT BESGI-IRANKTER HAFTUNG, or -FRA1\TKFORT-ON-THE-MAIN,

Patented Jan. 5, 1915.

GERMANY.

INSULATING MATERIAL.

1,123,985. Specification 0f Letters Patent. No Drawing.

To all whom it may concern Be it known that I, FRIEDRICH Bonmnc,engineer, citizen of Germany, and resident of Oberursel, nearFrankfort-on-the-Main, Germany, have invented certain new and usefulImprovements in, Insulating Materials, of which the following is aspecification. 1

My invention relates to a process for manufacturing heat proof, electricinsulating blades, plates, etc from mica waste and the like. I 1 r It isknown to produce electric insulating blades, plates, etc., from micawaste, flake mica, split mica, mica powder and the like, thesematerialsbeing far cheaper than the natural mica, the price of which isconstantly increasing, so that it becomes almost prohibitive for certainarticles.

The mica Waste or the like is united to bodies of the form required byusing a binding agent and subjecting the mixture to high pressure andhigh temperature at the same time. The binding agents which have beenused or suggested consist of shellac and other carbonaceous materials orof water- All these binding agents can however only be employed, if theinsulating bodies so made are not to withstand temperatures higher thansay about 150 C. At higher temperatures the carbonaceous materialsbecome softand charred, develop malodorous vapors and lose their bindingand insulating capacities. Waterglass on the other hand gives up itswater at said temperature and disintegrates into the form of a powderwhich no longer possesses any binding qualities and absorbs moisturefrom the atmosphere, thus unfavorably affecting the insulatingproperties of themica bodies to be produced.

Now, on the contrary to the methods referred to before, my process hasfor its object the manufacture of electric insulating blades, plates,etc., from mica wasteand the like, whichare capable of withstandingtemperatures up to 900 0. without any deleterious effect and withoutbeing inferior to 4 the natural mica as regards insulatin power,hardness and cleavage. Such insulating bodies are especially qualifiedfor use with electric cooking vessels, flat irons and similar apparatus,where they have to withway Applieation'filed May 31, 1913. Serial No.770,945.

stand, as is well known, temperatures up to 400 C. and more, for I someconsiderable tune and not only temporarily.

In addition to the Well known steps to combine the initially loose micaparticles by means of a binding" agent under an elevated temperature andhigh pressure. my new process oifers the distinctive feature, that,

the mixture of mica Waste or the like and blndlng agent is heated from500 to 950 C. and that a binding agent is used consisting of aninorganiccompound and having a meltlng point from 500 to 950 0. Such compoundsare for instance employed as customary in the manufacture of micanite,

after which they are submitted simultaneously to great pressure and to ahigh temperature. Any suitable pressure may be em ployed, and thetemperature will be just sufficiently high to melt completely thebinding or fiuxing material without deleteriously affecting itsqualities orthose of the mica. In another method of working, a layer ofthin mica is covered with the binding or fiuxing material and then micadust, which is a very cheap substance, is strewed over the surface. aWhen the desired thickness has been built up a covering sheet of splitmica is laid over the top and the whole is pressed apd heated as abovementioned. A number of successive layers made in this may be used toform a plate or block of any desired thickness. a

I claim:

1. An insulating material of the character described, consisting of micaflakes pasted stroyed when heated to this temperature substantially asand for the purpose set forth.

2. An insulating material of the character described consisting of micaflakes pasted together under high pressure by a fiuxing materialcontaining boron, silicon,

pressure, substantially as andfor the purpose set forth.

4:. The process of making an insulating material of the clfaracterdescribed, which consists in mixing mica flakes with 'a fluxing materialcontaining boron, silicon and lead and having a melting point between500 and 950 C, heating the mass to said temperatures, and subjecting itat the same time to high pressure, substantially as and for the purposeset forth.

In testimbny whereof I aiiix my signature in presence of two witnesses;

FRIEDRICH BULLING.

Witnesses JEAN GRUND, CARL GRUND.

